1. Field of the Invention
The invention relates to the field of transfer switches, and in particular concerns a transfer switch mechanism for transferring a power-consuming load reversibly between a pair of electric circuits.
2. Prior Art
Transfer switches are known in the art. Transfer switches operate, for example, to transfer a power consuming load from a circuit with a normal power supply to a circuit with an auxiliary power supply. Applications for transfer switches include stand-by applications, among others, in which the auxiliary power supply stands-by if the normal power supply should fail.
A transfer switch typically comprises a pair of circuit interrupters combined with a drive input and a linkage system. The preferred types of circuit interrupters have been the molded-case switches and molded-case circuit breaker type because these types are commercially available in a wide array of sizes and are relatively economical compared to other options. The preferred type of drive input depends on the application for the transfer switch. Usually motors are preferred, but other times there is a clear preference for manually-operated mechanisms.
As for the linkage system, there is a great variety in the prior art, and in all their variety known linkage systems are relatively involved and complex. The linkage system extends from the drive input to the handle of the circuit interrupter. Its function is to couple the drive input with the handle of the circuit interrupter so that drive force from the drive input is translated into position changes between progressive positions in the handle. Examples are shown by the U.S. Pat. Nos. 5,081,367--Smith et al., 4,760,278--Thomson and 4,398,097--Schell et al.
While known transfer switches include motor or manually-operated linkage systems for operating circuit interrupter handles, known linkage systems are deficient for numerous reasons. They generally are deficient in providing adequate mechanical advantage. Large circuit interrupters, for example, may require a 150 to 300 pound force to operate the handle between the CLOSED and OPEN position. Such handles are very difficult for electricians to operate without some kind of mechanical advantage.
Known motor or manually-operated linkage systems typically have a handle-engaging joint between the distal end and the handle, but the known joints are not adequately stiff. The joints are prone to twisting between the handle and the joint as the handle requires relatively greater force for operation. Twisting is likely to cause inelastic parts to fail or elastic parts to deform.
Furthermore, known motor or manually-operated linkage systems fail to incorporate any mechanism for enabling the advance of the circuit interrupter handles in short increments, without losing forward progress.
Further still, known motor or manually-operated linkage systems involve relatively elaborate mounting structures to couple together with commercially standard molded-case circuit switches and/or molded-case circuit breakers. Indeed, the known motor or manually-operated linkage systems characteristically are relatively costly and complicated structures to manufacture. What is needed is an improvement which overcomes the deficiencies in the prior art.